mather



(No Model.) 2 SheetsSheet l.

W. MATHER & J. & E. HOPKINSON.

DYNAMO ELECTRIC MACHINE.

N0. 30,180. Patented Sept. 25, 1888.

(No Model.) 2 Sheets-Sheet 2.

W. MATHER & J. & B. HOPKINSON.

D YNAMO ELECTRIC MACHINE.

No. 390,180. Patented Sept. 25, 1888.

UNITED STATES PATENT Orricn.

IVILLIAM MATHER AND EDWARD HOPKINSON, OF MANCHESTER, COUNTY OF LAN (EASTER, AND JOHN HOPKINSON, OF XVESTMINSTER, ENGLAND.

DYNAMO-ELECTRlC MACl-HNE.

SPECIFICATION forming part of Letters Patent No. 390,180, dated Sept-ember 25,1888. Application filed September 19, 1887. Serial No. 250,110. (No model.) Patented in England November .17, 18 4, No.l5,0-l8,

To aZZ whom it may concern..-

Be it known that we, WILLIAM llIATIIER, engineer, JOHN HorKINsoN, F. R. S., and EDWARD HorKINson, engineer, subjects of 5 the Queen of Great Britain and Ireland, and residing, respectively, WILLIAM llL'LTHER at The Sall'ord Iron \Vorks, Manchester, in the county of Lancaster, England, JoIIN HOPKIN SON at I \Vestminstcr Chambers, in the city of WVestminster, England, and EDWARD Hor- KINSON' at The Salt'ord Iron Works aforesaid, have jointly invented certain new and useful Improvements in Dynamo-Electric Machines, (for which we have obtained a patent in Great Britain, No. 15,648, dated November 27, 1884,) of which the following is a specification.

Our invention relates to improvements in dynamo-electric machines, and more particularly to that class of such machines wherein the armature is of the type commonly known as a gramme ring, or of the earlier form known as the Pacinotti ring. lVe greatly augment the intensity of the magnetic field and thereby the output of the machine by increasing the section ofiron in the magnets and polepieces beyond the section that has hitherto been used in machines of this class. To the same end we construct the armature so that the section of iron is not much less than the section in the magnets, thereby insuring that the magnetic induction is not restricted by reason of the iron becoming too rapidly saturated. lVe are thus able to obtain at low cost a field of not much inferior intensity to that obtained in the improved form of Edison machine, for which British Letters Patent No. 973, dated February 22, 1883, were granted to one of us, namely, John Hopkinsou. In order to reduce the weight of the pole-pieces, we may construct them so that their boundinglines are approximately coincident with the lines of magnetic induction, and by special polar extensions (explained hereinafter in reference to the drawings) we produce a weak field near the neutral point capable of controlling any tendency to sparking at the commutator.

In that form of our machine wherein the magnetic circuit is formed partly of cast'iron and partly of wrought-iron we so apportion the section of the two metals and their surface Hopkinson.

Our improvements are equally applicable, whether the dynamoelectric machine be used for the generation of the electric current or for 6 the conversion of electrical into mechanical power.

In order that our invention may be better understood, we refer to the accompanying drawings, wherein- 0 Figure lshows the armature in longitudinal section, while Fig. 2 shows a crosssection, together with one arrangement of magnets having a single magnetic circuit. Figs. 3 and 3" show an elevation and a plan of the same machine. Figs. 4-, 5, and 6 show the several views of a dynamo constructed with a double magnetic circuit, Fig. 4 bcinga cross-section, Fig. 5 a side elevation, and Fig. (3 a plan. Fig. 7 shows the extension of the polepicccs, whereby the field at the neutral point is controlled.

It will be understood that all the figures are to a certain extent diagrammatiqas details of construction which are not necessary to the explanation of this invention are omitted.

In all the figures, (Ht represent the shaft; Z), the commutator; c, a boss with arms 0 to carry the core (I, which consists of soft irou plates or wire continuous in the direction of the 0 lines of force but divided into sections in the direction of the length of the armature by paper or other insulator. The curved form of the pole-pieces, to avoid useless weight, is shown in Fig. 2, the boundary-line being approximately coincident with the line of magnetic induction. The pole-pieces c 6 may be of cast-iron, and the magnet-limbs ff of wrought-iron. Ive let the latter into the polepieces, as shown in the section, to secure 10o that at no part of the cast-iron shall the sectional area be less than at least half as much again as the sectional area of the wrought-iron cores.

In the double magnetic-circuit form of ma chine shown in Figs. 4, 5, and 6 we, for convenience,extend the under yoke or pole-pieces to form the base of the machine, to which the pedestals carrying the bearings of the armatureshaft are bolted. To restrict theleakage ofmagnetic field, we make the pedestals of nonmagnetic material or separate them from the base by a plate of non-magnetic material.

The extension of the pole-piece shown at e in Fig. 7 is of small sectional area compared with the other parts of the pole-piece. The said extensions 0" are integral parts of the pole'pieces. The area of the extensions may be further reduced by making the polar extension extend only through a portion of the depth of the pole-pieee-that is to say, the extension 6 does not extend entirely across the pole the full length of the armature, but embraces a portion only of the length of the armature. By this construction we produce a weak field near the neutral point, and thus control any tendency to sparking at the commutator.

Heretofore the pole-pieces of field-magnets have been made to embrace more or less of the periphery of the armature, and have in some instances been tapering in form toward the neutral point. The polar extensions of the present invention difl'er from such previous devices both in purpose and construction. The pole does not taper gradually and uniformly toward the neutral point-that is, the polar extensions do not merge imperceptibly into the poles proper, but are throughout of small sectional area compared therewith. This coir struction is essential to effect the purpose above stated.

In order to avoid the cost of making the turned core of the magnet and the bore of the hole in the yoke a precise fit, we may sometimes make use of a tightening set-screw, m m, by means of which we bring the opposed surfaces of core and yoke through which the lines of magnetic force pass into contact, leaving the shaft a loose fit in other parts.

Having now described and particularly ascertained the nature of our invention and the manner in which the same is or may be used or carried into effect, we declare that what we claim is- 1. In a dynamo-electric machine, the combination, with the armature, of the field-magnets, comprising solid wrought-iron cores,and cast-iron poles of much greater sectional area than said cores, the latter being let into the former and being at their ends entirely surrounded by the metal forming the poles, substantially as described.

2. The combination, with the armature, of the pole-pieces having curved boundinglines approximately coincident with the lines of magnetic induction and provided with special polar extensions of small sectional area compared with the poles proper, substantially as and for the purpose set forth.

In testimony whereof we have signed our names to this specification in the presence of two subscribing witnesses.

WVILLIAM MATHER. JOHN HOPKINSON. ED\VARD HOPKINSON.

Vitnesses to the signature of \Villiam Mather:

E. BUTLER RoWLEY,

Solicitor, Manchester. Geo. W. BROWN, Clerk with E. Butler Rowley, 2 Booth Street,

lllaachester. \Vitnesses to the signature of John Hopkinson:

E. BUTLER RowLEY,

Solicitor, Manchesier. W. WARDLE,

His Clerk. Witnesses to the signature of Edward Hopkinson:

SYDENHAM PAYNE, Solicitor, Dover.

J OHN Warrs,

37 High Street, Dover. 

